This invention relates to improvements in remotely controlled actuator mechanisms requiring two independent modes of motion and, more particularly, relates to an improved push-pull cable system for shifting gears in a vehicle transmission by operation of a gearshift lever remotely located from the transmission.
In the present state of the art in situations in which a vehicle transmission is remotely located from the vehicle operator, such as in a cab-over design track or in a bus with a rear engine, systems of torque tubes and rigid links are used to transmit control motion of the gearshift lever by the operator to the vehicle transmission. In order to simplify installation of the transmission control mechanism it is possible to utilize flexible coaxial push-pull cables to operate the transmission mechanism by remote control.
When using flexible push-pull cables for such remote actuation of the transmission, cable friction and backlash are important factors to be considered. Also, it is necessary to fit the linkage system into a relatively small and predetermined space envelope. Typically, two independent modes of motion are used in controlling the transmission, motion in one mode being used to select the gear rail on which the desired gears are located in the transmission and the second mode of motion being utilized to actually shift the transmission to the desired gears. In order to obtain proper operation of the transmission, it is necessary to keep the motion in the two modes independent of each other and any linkage that is used to transfer motion from the operator to the transmission must minimize interaction between motion in the two modes.